Atomic Physics
Attoclock revisited on electron tunnelling time (1901.07015v2)
C. Hofmann, A. S. Landsman, U. Keller
2019-01-21
The last decade has seen an intense renewed debate on tunnelling time, both from a theoretical and an experimental perspective. Here, we review recent developments and new insights in the field of strong-field tunnel ionization related to tunnelling time, and apply these findings to the interpretation of the attoclock experiment [Landsman et al., Optica 1, 343 (2014)]. We conclude that models including finite tunnelling time are consistent with recent experimental measurements.
Photoionization of Rb
ions in the valence energy region 37 eV -- 44 eV (1904.10770v2)
Brendan M McLaughlin, James F Babb
2019-04-24
Absolute photoionization cross sections for the Rb
2.5 meV bandwidth illustrated multiple Rydberg resonance series associated with the ground and metastable states. Here we present theoretical cross section results obtained using the Dirac-Coulomb
-matrix approximation with a detailed analysis of the resonances. The calculations were performed for the
,
ground state and the corresponding
metastable level. Results from the large-scale calculations are benchmarked against the \textsc{als} high-resolution measurements and reproduce the dominant resonance features in the spectra, providing confidence in the theoretical work for astrophysical applications.
Interactions between non-resonant rf fields and atoms with strong spin-exchange collisions (1812.03772v2)
Chuanpeng Hao, Zheru Qiu, Qi Sun, Yuan Zhu, Dong Sheng
2018-12-10
We study the interactions between oscillating non-resonant rf fields and atoms with strong spin-exchange collisions in the presence of a weak dc magnetic field. We find that the atomic Larmor precession frequency shows a new functional form to the rf field parameters when the spin-exchange collision rate is tuned. In the weak rf field amplitude regime, a strong modification of atomic Larmor frequency appears when the spin-exchange rate is comparable to the rf field frequency. This new effect has been neglected before due to its narrow observation window. We compare the experimental results with density matrix calculations, and explain the data by an underdamped oscillator model. When the rf field amplitude is large, there is a minimum atomic gyromagnetic ratio point due to the rf photon dressing, and we find that strong spin-exchange interactions modify the position of such a point.
Experimental realization of a momentum-space quantum walk (1809.09282v3)
Siamak Dadras, Alexander Gresch, Caspar Groiseau, Sandro Wimberger, Gil S. Summy
2018-09-25
We report on a discrete-time quantum walk that uses the momentum of ultra-cold rubidium-87 atoms as the walk space and two internal atomic states as the coin degree of freedom. Each step of the walk consists of a coin toss (a microwave pulse) followed by a unitary shift operator (a resonant ratchet pulse). We carry out a comprehensive experimental study on the effects of various parameters, including the strength of the shift operation, coin parameters, noise, and initialization of the system on the behavior of the walk. The walk dynamics can be well controlled in our experiment; potential applications include atom interferometry and engineering asymmetric walks.
Experimental limit on an exotic parity-odd spin- and velocity-dependent interaction using an optically polarized vapor (1902.00128v2)
Young Jin Kim, Ping-Han Chu, Igor Savukov, Shaun Newman
2019-01-31
Exotic spin-dependent interactions between fermions have recently attracted attention in relation to theories beyond the Standard Model. The exotic interactions can be mediated by hypothetical fundamental bosons which may explain several unsolved mysteries in physics. Here we expand this area of research by probing an exotic parity-odd spin- and velocity-dependent interaction between the axial-vector electron coupling and the vector nucleon coupling for polarized electrons. This experiment utilizes a high-sensitivity atomic magnetometer, based on an optically polarized vapor that is a source of polarized electrons, and a solid-state mass containing unpolarized nucleons. The atomic magnetometer can detect an effective magnetic field induced by the exotic interaction between unpolarized nucleons and polarized electrons. We set an experimental limit on the electron-nucleon coupling
at the mediator boson mass below
eV, significantly improving the current limit by up to 17 orders of magnitude.
Momentum-space atom correlations in a Mott insulator (1904.10995v1)
Cécile Carcy, Hugo Cayla, Antoine Tenart, Alain Aspect, Marco Mancini, David Clément
2019-04-24
We report on the investigation of the three-dimensional single-atom-resolved distributions of bosonic Mott insulators in momentum-space. Firstly, we measure the two-body and three-body correlations deep in the Mott regime, finding a perfectly contrasted bunching whose periodicity reproduces the reciprocal lattice. In addition, we show that the two-body correlation length is inversely proportional to the in-trap size of the Mott state with a pre-factor in agreement with the prediction for an incoherent state occupying a uniformly filled lattice. Our findings indicate that the momentum-space correlations of a Mott insulator at small tunnelling is that of a many-body ground-state with Gaussian statistics. Secondly, in the Mott insulating regime with increasing tunnelling, we extract the spectral weight of the quasi-particles from the momentum density profiles. On approaching the transition towards a superfluid, the momentum spread of the spectral weight is found to decrease as a result of the increased mobility of the quasi-particles in the lattice. While the shapes of the observed spectral weight agree with the ones predicted by perturbative many-body calculations, the fitted mobilities are larger than the theoretical ones. This discrepancy is similar to that previously reported on the time-of-flight visibility.
Seconds-scale coherence in a tweezer-array optical clock (1904.10934v1)
Matthew A. Norcia, Aaron W. Young, William J. Eckner, Eric Oelker, Jun Ye, Adam M. Kaufman
2019-04-24
Optical clocks based on atoms and ions achieve exceptional precision and accuracy, with applications to relativistic geodesy, tests of relativity, and searches for dark matter. Achieving such performance requires balancing competing desirable features, including a high particle number, isolation of atoms from collisions, insensitivity to motional effects, and high duty-cycle operation. Here we demonstrate a new platform based on arrays of ultracold strontium atoms confined within optical tweezers that realizes a novel combination of these features by providing a scalable platform for isolated atoms that can be interrogated multiple times. With this tweezer-array clock, we achieve greater than 3 second coherence times and record duty cycles up to 96%, as well as stability commensurate with leading platforms. By using optical tweezer arrays --- a proven platform for the controlled creation of entanglement through microscopic control --- this work further promises a new path toward combining entanglement enhanced sensitivities with the most precise optical clock transitions.
Full quantum analysis of complete population transfer using frequency boost (1904.10841v1)
Fatemeh Ahmadinouri, Mehdi Hosseini, Farrokh Sarreshtedari
2019-04-24
In this paper, we have proposed and demonstrated a new method of atomic population transfer. Transition dynamic of a two-level system is studied in a full quantum description of the Jaynes-Cummings model. Solving the time-dependent Schr"odinger equation, we have investigated the transition probabilities numerically and analytically by using a sudden boost of the laser frequency. The results show that complete population transfer can be achieved by adjusting the time of the frequency boost.
Visualizing entanglement in atoms and molecules (1809.05431v3)
B. I. Davies, R. P. Rundle, V. M. Dwyer, J. H. Samson, Todd Tilma, M. J. Everitt
2018-09-14
In this work we show how constructing Wigner functions of heterogeneous quantum systems leads to new capability in the visualization of quantum states of atoms and molecules. This method allows us to display quantum correlations (entanglement) between spin and spatial degrees of freedom (spin-orbit coupling) and between spin degrees of freedom, as well as more complex combinations of spin and spatial entanglement for the first time. This is important as there is growing recognition that such properties affect the physical characteristics, and chemistry, of atoms and molecules. Our visualizations are sufficiently accessible that, with some preparation, those with a non-technical background can gain an appreciation of subtle quantum properties of atomic and other systems. By providing new insights and modelling capability, our phase-space representation will be of great utility in understanding aspects of atomic physics and chemistry not available with current techniques.
An extended locally constant field approximation for nonlinear Compton scattering (1808.10339v2)
A. Ilderton, B. King, D. Seipt
2018-08-30
The locally constant field approximation (LCFA) has to date underpinned the numerical simulation of quantum processes in laser-plasma physics and astrophysics, but its validity has recently been questioned in the parameter regime of current laser experiments. While improvements are needed, literature corrections to the LCFA show inherent problems. Using nonlinear Compton scattering in laser fields to illustrate, we show here how to overcome the problems in LCFA corrections. We derive an "LCFA+" which, comparing with the full QED result, shows an improvement over the LCFA across the whole photon emission spectrum. We also demonstrate an implementation of our results in the type of numerical code used to design and analyse intense laser experiments.